Linear Technology LTC3703, Manual

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LTC3703-5
1
37035fa
APPLICATIO S
U
DESCRIPTIO
U
FEATURES
TYPICAL APPLICATIO
U
■ High Voltage Operation: Up to 60V
■ Large 1
Ω
Gate Drivers (with 5V Supply)
■ No Current Sense Resistor Required
■ Step-Up or Step-Down DC/DC Converter
■ Dual N-Channel MOSFET Synchronous Drive
■ Excellent Line and Load Transient Response
■ Programmable Constant Frequency: 100kHz to
600kHz
■
±
1% Reference Accuracy
■ Synchronizable up to 600kHz
■ Selectable Pulse Skip Mode Operation
■ Low Shutdown Current: 25
µ
A Typ
■ Programmable Current Limit
■ Undervoltage Lockout
■ Programmable Soft-Start
■ 16-Pin Narrow SSOP and 28-Pin SSOP Packages
The LTC
®
3703-5 is a synchronous step-down switching
regulator controller that can directly step-down voltages
from up to 60V input, making it ideal for telecom and au-
tomotive applications. The LTC3703-5 drives external logic
level N-channel MOSFETs using a constant frequency (up
to 600kHz), voltage mode architecture.
A precise internal reference provides 1% DC accuracy. A
high bandwidth error amplifier and patented* line feed
forward compensation provide very fast line and load
transient response. Strong 1
Ω
gate drivers allow the
LTC3703-5 to drive multiple MOSFETs for higher current
applications. The operating frequency is user program-
mable from 100kHz to 600kHz and can also be synchro-
nized to an external clock for noise-sensitive applications.
Current limit is programmable with an external resistor
and utilizes the voltage drop across the synchronous
MOSFET to eliminate the need for a current sense resistor.
For applications requiring up to 100V operation, refer to
the LTC3703 data sheet.
60V Synchronous
Switching Regulator Controller
Efficiency vs Load Current
High Efficiency High Voltage Step-Down Converter
LTC3703-5
MODE/SYNC
FSET
COMP
FB
I
MAX
INV
RUN/SS
GND
V
IN
BOOST
TG
SW
VCC
DRV
CC
BG
BGRTN
22
µ
F
×
2
1000pF
2200pF
10k
100
Ω
113k
1%
21.5k
1%
10
Ω
12k
30k
0.1
µ
F
V
IN
6V TO 60V
8
µ
H
D1
MBR1100
V
OUT
5V
5A
270
µ
F
16V
MMDL770T1
V
CC
5V
0.1
µ
F
37035 TA04
10
µ
F
1
µ
F
+
+
+
Si7850DP
Si7850DP
22
µ
F
470pF
LOAD CURRENT (A)
0
EFFICIENCY (
%
)
100
95
90
85
80
4
37053 TA04b
1 2 3 5
V
IN
= 12V
V
IN
= 42V
V
IN
= 24V
■ 48V Telecom and Base Station Power Supplies
■ Networking Equipment, Servers
■
Automotive and Industrial Control
PARAMETER LTC3703-5 LTC3703
Maximum V
IN
60V 100V
MOSFET Gate Drive 4.5V to 15V 9.3V to 15V
V
CC
UV
+
3.7V 8.7V
V
CC
UV
–
3.1V 6.2V
, LTC and LT are registered trademarks of Linear Technology Corporation.
All other trademarks are the property of their respective owners.
*U.S. Patent Numbers: 5408150, 5055767, 6677210, 5847554, 5481178, 6304066, 6580258;
Others Pending.